Make 55 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 55. 55 cannot be made with + - × ÷ alone (the solver checked every expression) — you will need to stick 9s together (like 99) or use decimals (like .9).

Solutions using only + - × ÷

No expression made of four plain 9s and + - × ÷ reaches 55 — the solver checked every possible expression.

Solutions with concatenation and decimals

99 / (.9 + .9) = 55

Solutions with square roots, factorials, exponents

9 × sqrt(9)! + 9 / 9 = 55
.9 / .9 + 9 × sqrt(9)! = 55
9! / 9! + 9 × sqrt(9)! = 55
(9 - 9)! + 9 × sqrt(9)! = 55
(9! / sqrt(9)!! - 9) / 9 = 55

…and 11 more at this tier.

17 distinct solutions found in total, after removing trivial rearrangements.

Make 54 with four 9s · Make 56 with four 9s

The Number Lab

Same idea, different constraints: four 9s, four 4s, or any four digits you like.

Four Nines — the daily puzzle
Four Nines solver — every target, solved
Four Fours — the 1881 original
Four Fours solver — including the impossible five
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Today's 24 — one new hand a day

Play the daily Four Nines puzzle, pick another number in the solver, or find more free math games.